JavaScript is disabled for your browser. Some features of this site may not work without it.

The impact of recall bias on the accuracy of dietary information

Van Zyl, Zoe (2014-04)

Thesis (MNutr)--Stellenbosch University, 2014.

Thesis

ENGLISH ABSTRACT: Background: A number of observational studies where information was obtained
retrospectively have been used in the past to inform guidelines regarding allergy prevention.
Studies looking at the causative/protective properties of infant dietary factors on diseases
that occur later in life also rely on maternal recall many years later. It is unclear however
what the effect of the recall bias was on the accuracy/quality of the information obtained.
Objectives: The aim of the study was to determine the impact of recall bias 10 years
retrospectively on the accuracy of dietary information in relation to breast feeding, weaning
age and introduction of allergenic foods. A literature review was performed into studies
assessing the accuracy of data obtained retrospectively and into studies using retrospective
data to draw conclusions on the protective/causative factors of infant feeding in relation to
food allergy.
Methodology: An infant feeding questionnaire was developed from some of the same
questions that were asked by mothers recruited into the FAIR study, a prospective birth
cohort on the Isle of Wight. Families had been recruited and followed up since 2001/2002
and data has been gathered when the mothers were 36 weeks pregnant, and then when
their child was 3, 6, 9 months and 1 and 2 years old. Mothers were asked in 2012, when their
children were 10 years of age, to complete this questionnaire. Agreement of answers was
computed using Kappa coefficients, Spearman’s correlation and percentage agreement. Results: One hundred and twenty five mothers completed the questionnaire. There was
substantial agreement for recall of whether mothers breast fed, the duration of EBF and
breast feeding 10 years earlier (k = 0.79, r = 0.70 and r = 0.84 respectively). Seven per cent
(n = 9) of mothers however who did breast feed reported not to have. Eighty four per cent (n
= 103) of mothers recorded correctly whether their child had a bottle of formula milk in
hospital. Ninety four per cent (n = 116) of mothers recalled accurately that their child had
received formula milk at some stage of their infancy. The exact age at which formula milk
was first given to their child was answered accurately (r = 0.63). The brand of formula milk
provided was poorly recalled. Answers to when mothers first introduced solid foods into their child’s diet were not accurate (r = 0.16). The age of introduction of peanuts was the
only food allergen that mothers recalled accurately for when they first introduced this into
their child’s diet (86% correct answers). Recall of whether peanuts were consumed during
pregnancy was accurate after two years (k = 0.64) but not after 8 years (k = 0.39).
Conclusion: The study highlights the importance of possible recall bias of infant feeding
practices by mothers over a period of 10 years. Recall related to breast feeding and formula
feeding were accurately recorded for, but not for age of introduction of solid foods and
introduction of allergenic foods. Studies relying on maternal recall of weaning questions
need to be cautious.